Mobile station association procedures with type II relays

ABSTRACT

A relay node including one or more components configured to measure a signal strength of sounding reference signals (SRS) received from a mobile station, and in response to the signal strength being above a predetermined threshold, to transmit a first request to an access node. The first request is for the access node to associate the mobile station with the relay node.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority to U.S. provisional patentapplication No. 61/218,910 filed Jun. 19, 2009, by Yi Yu, et al,entitled “Mobile Station Association Procedures with Type II Relays”(35773-1-US-PRV-4214-19000), which is incorporated by reference hereinas if reproduced in its entirety.

BACKGROUND

As used herein, the terms “mobile station” (“MS”), “user agent” (“UA”),and “user equipment” (“UE”) might in some cases refer to mobile devicessuch as mobile telephones, personal digital assistants, handheld orlaptop computers, and similar devices that have telecommunicationscapabilities. Such a MS might consist of a MS and its associatedremovable memory module, such as but not limited to a UniversalIntegrated Circuit Card (UICC) that includes a Subscriber IdentityModule (SIM) application, a Universal Subscriber Identity Module (USIM)application, or a Removable User Identity Module (R-UIM) application. Asused herein, the term “SIM” may also refer to “USIM” and the term “USIM”may also refer to “SIM.” Alternatively, such a MS might consist of thedevice itself without such a module. In other cases, the term “MS” mightrefer to devices that have similar capabilities but that are nottransportable, such as desktop computers, set-top boxes, or networkappliances. The term “MS” can also refer to any hardware or softwarecomponent that can terminate a communication session for a user. Also,the terms “MS,” “UE,” “user agent” (“UA”), “user device” and “user node”might be used synonymously herein.

As telecommunications technology has evolved, more advanced networkaccess equipment has been introduced that can provide services that werenot possible previously. This network access equipment might includesystems and devices that are improvements of the equivalent equipment ina traditional wireless telecommunications system. Such advanced or nextgeneration equipment may be included in evolving wireless communicationsstandards, such as long-term evolution (LTE) or LTE-Advanced (LTE-A).For example, LTE or LTE-A systems might include an Evolved UniversalTerrestrial Radio Access Network (E-UTRAN) node B (eNB), a wirelessaccess point, or a similar component rather than a traditional basestation.

As used herein, the term “access node” will refer to any component ofthe wireless network, such as a traditional base station, a wirelessaccess point, or an LTE or LTE-A eNB, that creates a geographical areaof reception and transmission coverage allowing a MS or a relay node toaccess other components in a telecommunications system. In thisdocument, the term “access node” may comprise a plurality of hardwareand software. An access node, core network component, or other device,may provide wireless communications resources in an area known as acell.

An LTE or LTE-A system can include protocols such as a Radio ResourceControl (RRC) protocol, which is responsible for the assignment,configuration, and release of radio resources between a MS and an accessnode or relay node or other LTE equipment. The RRC protocol is describedin detail in the Third Generation Partnership Project (3GPP) TechnicalSpecification (TS) 36.331.

The signals that carry data between MSs, relay nodes, and access nodescan have frequency, time, and coding parameters and othercharacteristics that might be specified by a network node. A connectionbetween any of these elements that has a specific set of suchcharacteristics can be referred to as a resource. The terms “resource,”“communications connection,” “channel,” and “communications link” mightbe used synonymously herein. A network node typically establishes adifferent resource for each MS or other network node with which it iscommunicating at any particular time.

The term “access node” may not refer to a “relay node,” which is acomponent in a wireless network that is configured to extend or enhancethe coverage created by an access node or another relay node. The accessnode and relay node are both radio components that may be present in awireless communications network, and the terms “component” and “networknode” may refer to an access node or relay node. A component mightoperate as an access node or a relay node depending on its configurationand placement. However, a component is called a “relay node” only if itrequires the wireless coverage of an access node or other relay node toaccess other components in a wireless communications system.Additionally, two or more relay nodes may used serially to extend orenhance coverage created by an access node.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of this disclosure, reference is nowmade to the following brief description, taken in connection with theaccompanying drawings and detailed description, wherein like referencenumerals represent like parts.

FIG. 1 is a block diagram illustrating a wireless communication systemusing a relay node, according to an embodiment of the disclosure.

FIG. 2 shows a communication procedure among a RN, eNB, and MME,according to an embodiment of the disclosure.

FIG. 3 shows exemplary pseudo-code for a RRCConnectionRequest message,according to an embodiment of the disclosure.

FIG. 4 shows a communication procedure among a RN, eNB, and MME,according to an embodiment of the disclosure.

FIG. 5 shows a communication procedure among a RN, eNB, and MME,according to an embodiment of the disclosure.

FIG. 6 shows communication among multiple MSs, RNs, and an eNB,according to an embodiment of the disclosure.

FIG. 7 shows a communication procedure among a MS, RN, and eNB,according to an embodiment of the disclosure.

FIG. 8 is a flowchart showing a method for initializing a type 2 RN.

FIG. 9 is a flowchart showing a method for associating a RN with a MS.

FIG. 10 is a flowchart showing a method for associating a RN with a MS.

FIG. 11 shows an example of a system that includes a processingcomponent suitable for implementing one or more embodiments disclosedherein.

DETAILED DESCRIPTION

It should be understood at the outset that although illustrativeimplementations of one or more embodiments of the present disclosure areprovided below, the disclosed systems and/or methods may be implementedusing any number of techniques, whether currently known or in existence.The disclosure should in no way be limited to the illustrativeimplementations, drawings, and techniques illustrated below, includingthe exemplary designs and implementations illustrated and describedherein, but may be modified within the scope of the appended claimsalong with their full scope of equivalents.

The following terms have the following definitions as used herein. Wheresuch terms are used in the 3GPP technical specifications (TS), theseterms are equivalent to the definitions provided in the 3GPP TS.

“CQI” is defined as “Channel Quality Indicator.”

“CRS” is defined as “Common Reference Signal.”

“DL” is defined as “DownLink.”

“DRX” is defined as “Discontinuous Reception.”

“EC” is defined as “Establishment Cause.”

“eNB” is defined as “Evolved Node B.”

“EoR” is defined as “ENB or RN.”

“L1 Relay” or “Layer 1 RN” are defined as “Layer 1 relay node”.

“L2 Relay” or “Layer 2 RN” are defined as “Layer 2 relay node”.

“L3 Relay” or “Layer 3 RN” are defined as “Layer 3 relay node”.

“LTE” is defined as “Long Term Evolution.”

“LTE-A” is defined as “LTE-Advanced.”

“MAC” is defined as “Medium Access Control.”

“MIB” is defined as “Master Information Block.”

“MME” is defined as “Mobility Management Entity.”

“NAS” is defined as “Non-Access Stratum.”

“PDCCH” is defined as “Physical Downlink Control Channel.”

“PHY” is defined as “PHYsical layer.”

“RA” is defined as “Random Access.”

“RACH” is defined as “Random Access CHannel.”

“RAR” is defined as “Random Access Response.”

“RN” is defined as “Relay Node.”

“RRC” is defined as “Radio Resource Control.”

“SIB” is defined as “System Information Block.”

“SRS” is defined as “Sounding Reference Signal.”

The embodiments described herein relate to use of relay nodes (RNs) in awireless communication network. The embodiments further relate toinitialization procedures of a RN. The embodiments also relate toprocedures for associating and/or disassociating a MS with RNs and/oreNB.

The embodiments provide for at least three different techniques forperforming an initialization procedure for a RN. In an embodiment, aneNB may send a RACH response to a RN in response to a detected RACHpreamble. When the RN sends back the RRCConnectionRequest message, theRN will identify itself to the eNB as an RN, as opposed to a MS, byadding a value to the Establishment Cause of the RRCConnectionRequest.In another embodiment, the RN may send the eNB anRRCConnectionSetupComplete message that is empty of content. In thismanner, the eNB knows that the RACH procedure is initiated by a RN, asopposed to a MS. In yet another embodiment, a predetermined set ofpreambles are allocated for RNs (out of the available RACH preamblesassociated with the eNB). Once the eNB detects that the allocated RACHpreamble belongs to the pool of RACH preambles reserved for RNs, the eNBmay not institute NAS setup procedures with the enhanced packet core(EPC). The eNB may also institute NAS setup procedures with the EPCappropriate to the type of the RN. In some other embodiments, theindication to differentiate a RN from an MS can be sent by othersignaling during the initialization procedure, besides those signalingdescribed above.

In the case of associating and/or disassociating a MS with a RN and/oreNB, at least three techniques may be used to accomplish associationand/or disassociation. Note that the MS may be associated with multipleRNs, and also an eNB. In one embodiment, association of a MS to a RN isbased on the received signal quality of the MS uplink SRS signal. Forexample, when the average received signal strength (or in general anyindicator representing the quality of reception, such as signal tointerference plus noise ratio (SINR)) of the SRS signal of an existingassociated MS is strong or stronger than some pre-defined threshold, theRN requests that the eNB associate the MS to the RN. In contrast, if theSRS signal quality becomes too weak or weaker than some pre-definedthreshold, the RN may request the eNB to disassociate the MS from theRNs.

The thresholds used by RN to determine if the reception quality of theSRS signal received from the MS is too strong or too weak can bestatically, semi-statically or dynamically configured by the eNB. Inanother embodiment, the RNs report the measured SRS signal strength tothe eNB and the eNB decides if the MS should be associated with any ofthe RNs and/or the eNB. In one embodiment, the decision at the eNB canbe based on comparing the relative signal strength of the SRS receivedat the RNs and the eNB. In another embodiment, association and/ordisassociation is based on the RACH signal. Association ordisassociation may be based on a combination of the quality of thesignal received directly from the MS and the relayed RACH preamble CQI.In yet another embodiment, a combination of the SRS signal strength andRACH preamble may be used to prompt the RN to request the eNB toassociate or disassociate a MS with the RN. In another embodiment, acombination of the SRS signal strength and RACH preamble relayed by theRNs to the eNB and those received directly at the eNB, may be used bythe eNB to decide if the MS should associate or disassociate with theRNs.

Although the embodiments contemplate connecting to, or use of, an eNB,the embodiments also contemplate connecting to, or use of, differenttypes of access nodes. Thus, as used herein, the term “eNB” may alsomean “access node,” which may include any type of access device in acommunications network. Examples of other types of access nodes includelayer 3 relay nodes, core networks, mobility management entities, andothers.

FIG. 1 is a block diagram illustrating a wireless communication system100 using a relay node 102, according to an embodiment of thedisclosure. Generally, the present disclosure relates to the use ofrelay nodes in wireless communications networks. Examples of a wirelesscommunication network includes LTE or LTE-Advanced (LTE-A) networks, andall of the disclosed and claimed embodiments could be implemented in anLTE-A network. The relay node 102 can amplify, repeat, demodulate,decode, re-encode, and/or re-modulate a signal received from a MS 110and cause the modified signal to be received at an access node 106. Insome implementations of a relay node 102, the relay node 102 receives asignal with data from the MS 110 and then generates a new signal totransmit the data to the access node 106. The relay node 102 can alsoreceive data from the access node 106 and deliver the data to the MS110. The relay node 102 might be placed near the edges of a cell so thatthe MS 110 can communicate with the relay node 102 rather thancommunicating directly with the access node 106 for that cell.

In radio systems, a cell is a geographical area of reception andtransmission coverage. Cells can overlap with each other. In the typicalexample, there is one access node associated with each cell. The size ofa cell is determined by factors such as frequency band, peaktransmission power levels, and channel conditions. Relay nodes, such asrelay node 102, can be used to enhance coverage within or near a cell,or to extend the size of coverage of a cell. Additionally, the use of arelay node 102 can enhance throughput of a signal within a cell becausethe MS 110 can access the relay node 102 at a higher data rate or alower transmission power than the MS 110 might use when communicatingdirectly with the access node 106 for that cell. Transmission at ahigher data rate within the same bandwidth creates higher spectrumefficiency, and lower power benefits the MS 110 by consuming lessbattery power.

Relay nodes, generally, can be divided into three groups: layer 1 relaynodes, layer 2 relay nodes, and layer 3 relay nodes. A layer 1 relaynode is essentially a repeater that can retransmit a transmissionwithout any modification other than amplification and slight delay. Alayer 2 relay node can demodulate/decode a transmission that itreceives, re-encode/modulate the result of the decoding, and thentransmit the modulated data. A layer 3 relay node may have full radioresource control capabilities and can thus function similarly to anaccess node. The radio resource control protocols used by a layer 3relay node may be the same as those used by an access node, and therelay node may have a unique cell identity typically used by an accessnode. A type 1 relay node can be defined such that it is a layer 3 relaynode with its own physical cell identification and a complete RRCprotocol stack. For the purpose of this disclosure, a relay node isdistinguished from an access node by the fact that a relay node requiresthe presence of at least one access node (and the cell associated withthat access node) and possibly other relay nodes to access othercomponents in a telecommunications system.

The illustrative embodiments are primarily concerned with type 2 relaynodes. A type 2 relay node is a layer 2 relay node defined with thefollowing characteristics: Type 2 relay node does not have a separatephysical cell identification from the access nodes and thus would notcreate any new cells. A type 2 relay node should be able to relayto/from legacy (LTE Release 8) MSs, and the legacy MSs should not beaware of the presence of a type 2 relay node. The embodiments may applyto other types of relay nodes as well.

In communication system 100, the links that allow wireless communicationcan be said to be of three distinct types. First, when the MS 110 iscommunicating with the access node 106 via the relay node 102, thecommunication link between the MS 110 and the relay node 102 is said tooccur over an access link 108. Second, the communication between therelay node 102 and the access node 106 is said to occur over a relaylink 104. Third, communication that passes directly between the MS 110and the access node 106 without passing through the relay node 102 issaid to occur over a direct link 112. The terms “access link,” “relaylink,” and “direct link” are used in this document according to themeaning described by FIG. 1.

FIG. 2 shows a communication procedure among a RN, eNB, and MME,according to an embodiment of the disclosure. RN 200, eNB 202, and MME204 are components in a wireless communication network. RN 200 maycorrespond to RN 102 in FIG. 1, and eNB 202 may correspond with accessnode 106, also in FIG. 1. MME 204 is a component of a core network,which may take the form of hardware, software, or a combination thereof.In the embodiments described with respect to FIG. 2, RN 200 is a type 2relay node. The embodiments shown in FIG. 2 may be used duringinitialization of a type 2 relay node.

In the embodiments described herein, RN 200 may not have a cellidentification separate from that of the serving eNB 202, and thus mightnot create any new cells. RN 200 may be able to relay communications toand from MSs that are compliant with release 8 of the 3GPP TS. However,a release 8 compliant MS may not be aware of the presence of RN 200.

An issue faced by RN 200 is initialization, which is the process ofinitially connecting RN 200 to the wireless communication network, whichmay begin with initially establishing communication with eNB 202. In anembodiment, the RN 200 performs a random access procedure similar to therandom access procedure performed by a MS when connecting to thewireless communication network. The random access procedure isparticularly suited for, but not limited to, those RNs that are mobileor nomadic, wherein the locations of the RNs are not fixed.

In an embodiment, the random access procedure proceeds as follows.First, the RN 200 registers with the eNB 202 when the RN 200 initiallyattempts to access the wireless communication network. Then, a uniqueset of RNTIs are assigned to the RN 200 by the eNB 202 in the donor orcurrent cell serving the RN 200. The identification of the RN 200 may beperformed through additional parameters during the RRC setup procedure.Similar to a MS, the RN 200 may be handed-over from another eNB or froma type 1 RN. If no MSs are served by the RN 200 for a predeterminedtime, then the RN 200 may enter idle mode. In this manner, ifapplicable, battery life for a mobile RN or a nomadic RN, or in generalany battery power operated RN, may be preserved. In an embodiment, onlythe eNB 202 to which the RN 200 is connected is aware of the existenceof the RN 200. Other devices in the wireless communication network maynot be aware of RN 200. While in idle mode, the RN may keep checking theDL transmission from the eNB and the UL RACH transmission from UEsperiodically. The periodic wake up cycle is controlled by the eNB. Onsensing reception on DL or UL, the RN may exit the idle mode as soon aspossible. The RN may have to initiate a RACH procedure with the eNB whenexiting the idle mode.

Thus, when the RN 200 is initially activated, the RN 200 behaves muchlike a MS. The RN 200 will randomly pick one of the allowed RACHpreambles and transmit during a randomly selected RACH allocation in anuplink sub-frame. In an embodiment, the RN 200 obtains DL framesynchronization before listening to the MIB 206 and SIB 1 208 from theeNB 202. RACH configuration parameters are known to the RN 200 afterlistening to SIB 2 210.

Returning to an exemplary initialization procedure, the RN 200 attemptsto access the network with a RACH, as shown at RACH message 212. Inresponse to a detected RACH preamble from the RN 200, the eNB 202 sendsa RACH response (RAR) 214 to the RN 200 allocating UL resources for theMS to initiate the RRC connection procedure. The RN 200 then initiates aRRC connection setup procedure, beginning by sending aRRCConnectionRequest message 216 to identify itself to the eNB 202 as aRN. A new value, such as “RN access” may be added to the EstablishmentCause (EC) in the RRCConnectionRequest message 216. This new valueinforms the eNB 202 that RN 200 is a RN, as opposed to a MS.

In response, the eNB 202 sends an RRCConnectionSetup message 218 to theRN 200. The RN 200 completes the initialization procedure by sending aRRCConnectionSetupComplete message 220 to the eNB 202.

FIG. 3 shows exemplary pseudo-code for a RRCConnectionRequest message,according to an embodiment of the disclosure. The pseudo-code 300 shownin FIG. 3 may be stored, generated, and/or executed in a RN, such as RN200 of FIG. 2, and transmitted to an eNB, such as eNB 202.

As described with respect to FIG. 2, a new “RN Access” value 302 hasbeen added to the EstablishmentCause of the RRCConnectionRequestmessage. An EstablishmentCause is a message that informs the receivingdevice one or more reasons for the connection request. By knowing thereason for the connection request, the eNB may appropriately process theincoming connection request.

In this case, the RN Access value 302 allows an eNB, such as eNB 202 ofFIG. 2, to know that the device transmitting the RRCConnectionRequestmessage is a RN, as opposed to a MS. Thus, the eNB may respondaccordingly and manage the transmitting device as a RN, as opposed to aMS. The RN access may have different values in different embodiments.Further, the present disclosure should not be limited only to thedetails of the message of FIG. 3, as other messages and formats mightalso be used in other embodiments.

FIG. 4 shows a communication procedure among a RN, eNB, and MME,according to an embodiment of the disclosure. The communicationprocedure shown in FIG. 4 is similar to the communication procedureshown in FIG. 2. Reference numerals in FIG. 4 that correspond toreference numeral used in FIG. 2 have similar properties. Theembodiments shown in FIG. 4 may be used during initialization of a type2 relay node.

In this embodiment, the eNB 202 may be informed that RN 200 is a RN, asopposed to a MS, by the content of the RRCConnectionSetupCompletemessage 220. If RRCConnectionSetupComplete message 220 contains noinformation that would be sent by a MS, then eNB 202 may be informedthat RN 200 is a RN, as opposed to a MS.

MSs normally send information to setup a NAS connection in theRRCConnectionSetupComplete message 220. In the case of a RN, however,the RRCConnectionSetupComplete message 220 may be a dummy message,containing no information. Therefore, the eNB 202 may use this detail todifferentiate whether the RACH procedure is initiated by a RN or a MS.In this embodiment, the eNB 202 receives the RRCConnectionSetupCompletemessage 220 and determines whether the sender is a RN or a MS based onthe content, or lack of content, in RRCConnectionSetupComplete message220. In an alternative embodiment, the RRCConnectionSetupCompletemessage 220 may contain some content or data that specifically informseNB 202 that RN 200 is a RN, as opposed to a MS. Further, the presentdisclosure should not be limited to the use ofRRCConnectionSetupComplete message 220, as other messages and formatsmight also be used in other embodiments.

FIG. 5 shows a communication procedure among a RN, eNB, and MME,according to an embodiment of the disclosure. The communicationprocedure shown in FIG. 5 is similar to the communication procedureshown in FIG. 2. Reference numerals in FIG. 5 that correspond toreference numeral used in FIG. 2 have similar properties. Theembodiments shown in FIG. 5 may be used during initialization of a type2 relay node.

For the embodiment shown in FIG. 5, a RACH preamble may be allocated inthe RACH message 212 in order to differentiate RN 200 from a MS duringinitialization with the eNB 202. Once the eNB 202 detects that the RACHpreamble belongs to the pool of RACH preambles reserved for RNs, the eNBmay not initiate NAS setup procedures or may initiate NAS procedureappropriate to the type of relay. The eNB 202 treats the connectingentity as a RN, as the connecting entity is RN 200. A dummy RRCconnection setup message can be used as handshake between the eNB 202and the RN 200.

The embodiments described with respect to FIGS. 1 through 5 includedexamples of a RN distinguishing itself from a MS to an eNB duringinitialization of the RN. The embodiments described with respect to FIG.6 and FIG. 7 include examples of a MS associating or disassociating witha type 2 relay nodes and/or eNB.

FIG. 6 shows communication among multiple MSs, RNs, and an eNB,according to an embodiment of the disclosure. Communication network 600includes an eNB 602 and a number of RNs, including RN0 604 and RN1 606.Communication network 600 also includes a number of MSs, including MS0608, MS1 610, MS2 612, MS3 614, and MS4 616. Communications resourcesamong the various devices of communication network 600 are shown bylightning symbols 618. In other embodiments, communication network 600may include more or fewer RNs, MSs, and eNBs, such as where devicesconnect directly to a core network or MME. In the embodiments describedwith respect to FIG. 7, RN0 604 and RN1 606 may be type 2 relay nodes.

Because a type 2 RN may not transmit its own CRS and does not have itsown cell identification, the decision of associating a MS with a RNshould be performed between an eNB and the RN. Due to MS mobility, theassociation should be updated from time-to-time to increase thelikelihood that the MS is associated with the most desirable RN or RNs.In some cases, the MS may be associated with multiple RNs to furtherimprove performance. In other words, there may be cooperativecommunication from multiple access nodes, such as eNBs and RNs.

In the embodiment described with respect to FIG. 6, MS association witha RN may be based on the MS's uplink SRS signal. When a MS with arelatively strong SRS signal or with SRS signal strength higher than apre-defined threshold with or without hysteresis margin is detected, theRN should transmit to the eNB an association request. An associationrequest may be a request to the eNB to associate the MS with the RN. Onthe other hand, when the SRS signal of an existing associated MS becomesrelatively weak, as determined by a predetermined threshold with orwithout hysteresis margin, the RN should transmit to the eNB adisassociation request. A disassociation request may be a request to theeNB to disassociate the MS with the RN. The thresholds with or withouthysteresis margin used by RN to determine if the SRS signal receivedfrom the MS is too strong or too weak can be statically, semi-staticallyor dynamically configured by the eNB. In another embodiment, the RNreports the measured SRS signal strength to the eNB and the eNB decidesif the MS should be associated with the RN (s) and/or the eNB. In oneembodiment, the decision at the eNB can be based on comparing therelative signal strength of the SRS received at the RN and the eNB. Ingeneral any signal quality indicator observed over the received SRScombined with the DL measurement reports from the UE can be used tocontinuously update the association of the MS with any of the nodes, eNBand RN(s).

The SRS signal may be used for this purpose because, in LTE orLTE-Advanced, the MS will continue to transmit uplink SRS for channelquality measurement and for uplink timing estimation purposes. Each MSin the donor cell has a unique SRS transmission configuration; forexample, transmission comb, SRS duration, SRS bandwidth, and others. TheeNB may forward these SRS configurations to one or more RNs in the donorcell. Then, the RN may monitor the transmissions in the SRS “channel”and determine which MSs are nearby.

In an embodiment, the association and disassociation should be updatedat a predefined periodicity or in an event-driven manner due to the factthat the MSs may be mobile. In the periodicity approach, the periodicitycould be signaled by the eNB. Based on the corresponding measurements,the eNB may make several types of associations.

One association type may be the MS being associated with only the eNB.In this case, the RN may not transmit to or detect from the MS any dataor signaling. This association type may be referred to as an “eNB-only”association.

Another association type may be the MS being associated with one or moreRNs. In this case, over-the-air transmission may be scheduled at theeNB. Information may be transparently relayed to the MS through the oneor more RNs. This association type may be referred to as “RN-only”association.

Yet another association type may be the MS being associated with boththe eNB and the one or more RNs. In this case, over-the-air transmissionmay be from the eNB and the one or more RNs, using coordinatedmultipoint transmissions. This association type may be referred to as“multi-association.”

For example, referring to FIG. 6, MS0 608 is only associated with theeNB 602, which corresponds to the eNB-only association described above.In contrast, MS1 610 and MS2 612 are associated only with the RNs RN0604 and RN1 606, which corresponds to the RN-only association describedabove. However, MS3 614 and MS4 616 are associated with both the eNB 602and with RN0 604 and RN1 606, which corresponds to the multi-associationdescribed above. In all three association types, the associations forthe MSs may be updated continuously, or at a predetermined periodicity,as the MSs physically traverse the network.

In an embodiment, the eNB 602 sends the SRS transmission controlinformation to each MS. Additionally, the eNB 602 sends the SRStransmission control information of each MS to the RNs, RN0 604 and RN1606. The SRS transmission control information may include the SRStransmission period, measurement quantity, the SRS configurations,uplink timing information, and other information. In turn, the RNs, RN0604 and RN1 606, receive and measure the uplink SRS transmissionsaccording to the transmission control information.

The eNB may program a RN to transmit a measurement report based on theoccurrence of one or more events. Examples of events include reaching athreshold, or expiration of a timer. The RN could also periodicallytransmit the measurement report without having been triggered to do so.The measurement report may include multiple users' measurement reports.The RN may also make timing estimates from the received SRStransmissions. The received SRS transmissions may also be used fortiming alignment adjustments. The RN may also make the UE associationdecision based on the measured SRS signal strength and report the UEassociation decision to the eNB.

In addition to the above information, the DRX configuration of a MS maybe forwarded to the one or more RNs. Forwarding the DRX configurationmay be helpful for release-8 MSs because these MSs may not transmit theSRS during the DRX off-durations. Thus, even for release-8 MSs, the oneor more RNs may perform suitable measurements of the MSs.

FIG. 7 shows a communication procedure among a MS, RN, and eNB,according to an embodiment of the disclosure. Communication procedure700 may be implemented among MSs in connection with one or more RNs,such as one or both of MS1 610 or MS2 612 are in connection with one orboth of RN0 604 or RN1 606 of FIG. 6.

In the embodiment described with respect to FIG. 7, MS association withan RN may be based on the initial random access signal. During initialaccess of the MS 702 to the eNB 706 via RN 704, the eNB 706 receives aRACH preamble from the MS 702. All close-by RNs, such as RN 704, alsoreceive the RACH preamble. The eNB 706 may then associate the MS 702 tothe RN 704, based on the quality of the signal received directly fromthe MS 702 and the relayed RACH preamble channel quality indicator (CQI)from the RN 704. The RN, such as RN 704 may also make the UE associationdecision based on the received RACH preamble signal and report theassociated UE identification to the eNB.

The eNB 706 may send signaling, such as a PDCCH order, MAC controlelement, or RRC signaling, to request the MS 702 to perform uplinkrandom access for the association. After the reception of the signalingfrom the eNB 706, the MS 702 will transmit the random access preamble.

In an embodiment, the MS 702 might not need to perform the full randomaccess procedure. For example, the SRS configuration forwarding message708 and the SRS message 710 may be enough to associate the MS 702 withthe RN 704.

In an alternative embodiment, MS association may be accomplished bycombining the SRS method (FIG. 6) and the random access preamble method(FIG. 7) described above. During the initial access by MS 702, the eNB706 may associate the MS 702 to the RN 704 or to the eNB 706, based onthe received preamble signal strength. After initial association, the MSassociation/disassociation may be performed and updated by the MS uplinkSRS transmission at SRS message 710.

FIG. 8 is a flowchart showing a method for initializing a type 2 RN. Theprocess shown in FIG. 8 may be implemented in a RN, such as RN 102 ofFIG. 1. The process shown in FIG. 8 may be implemented using proceduresdescribed with respect to FIG. 2 through FIG. 5. The method includesencoding a message identifying a type two relay node as a relay nodeupon initialization of the relay node (block 800). The processterminates thereafter.

In an embodiment the message may be an RRCConnectionRequest message. Inthis case a value may be added to an Establishment Cause in theRRCConnectionRequest message. The value identifies to an access nodethat the type two relay node is a relay node.

In another embodiment, the message is an RRCConnectionSetupCompletemessage. In this case, the type two relay node is identified to anaccess node as a relay node when the RRCConnectionSetupComplete isdevoid of content.

In yet another embodiment, the message comprises a random access channel(RACH) message. In this case, a preamble is allocated in the RACHmessage in order to identify to an access node that the type two relaynode is a relay node. The allocated preamble may be taken from a pool ofpredetermined preambles.

FIG. 9 is a flowchart showing a method for associating a RN with a MS.The process shown in FIG. 9 may be implemented in a RN, such as RN 102of FIG. 1. The process shown in FIG. 9 may be implemented usingprocedures described with respect to FIGS. 6 and 7.

The process begins as a RN measures a signal strength of soundingreference signals (SRS) received from a mobile station (block 900). TheRN then transmits, in response to the signal strength being above apredetermined threshold, a first request to an access node (block 902).The first request is for the access node to associate the mobile stationwith the relay node. The process terminates thereafter.

In an embodiment, the RN transmits a second request to the access nodeafter the first request. The second request is transmitted in responseto the signal strength falling below a second predetermined threshold.The second request is for the access node to disassociate the mobilestation with the relay node.

In another embodiment, the RN periodically measures the signal strength.In still another embodiment, the RN generates a measurement report ofthe signal strength upon satisfaction of a condition set by the accessnode. The condition may be one of a threshold of the signal strength andan expiration of a timer, or some other condition.

In still another embodiment, the first request establishes one type ofassociation selected from the group consisting of: the mobile stationbeing associated with the access node only, the mobile station beingassociated with one or more relay nodes only, and the mobile stationbeing associated with both the access node and the one or more relaynodes.

FIG. 10 is a flowchart showing a method for associating a RN with a MS.The process shown in FIG. 10 may be implemented in an access node, suchas access node 106 of FIG. 1. The process shown in FIG. 10 may beimplemented using procedures described with respect to FIGS. 6 and 7.

The process begins as the access node receives a signal from a mobilestation, wherein the signal has a signal strength (block 1000). Theaccess node also receives a relayed random access channel (RACH) requestfrom a relay node (block 1002). The relayed RACH request originated atthe mobile station and includes a preamble comprising a channel qualityindicator (CQI).

Next, the access node encodes a response message to be transmitted tothe mobile station (bock 1004). The response message is encoded toinstruct the mobile station to associate with the relay node via therandom access procedure.

In an embodiment, the response message is one of a physical downlinkcontrol channel (PDCCH) order, a media access layer (MAC) controlelement, or a radio resource control (RRC) signaling. In anotherembodiment, the response message may be encoded to instruct the mobilestation to transmit the preamble.

In still another embodiment, the response message may be encoded toinstruct the mobile station to associate with the relay node by usingless than a full random access procedure.

The MS and other components described above might include a processingcomponent that is capable of executing instructions related to theactions described above. FIG. 11 illustrates an example of a system 1115that includes a processing component 1110 suitable for implementing oneor more embodiments disclosed herein. In addition to the processor 1110(which may be referred to as a central processor unit or CPU), thesystem 1100 might include network connectivity devices 1120, randomaccess memory (RAM) 1130, read only memory (ROM) 1140, secondary storage1150, and input/output (I/O) devices 1160. These components mightcommunicate with one another via a bus 1170. In some cases, some ofthese components may not be present or may be combined in variouscombinations with one another or with other components not shown. Thesecomponents might be located in a single physical entity or in more thanone physical entity. Any actions described herein as being taken by theprocessor 1110 might be taken by the processor 1110 alone or by theprocessor 1110 in conjunction with one or more components shown or notshown in the drawing, such as a digital signal processor (DSP) 1190.Although the DSP 1190 is shown as a separate component, the DSP 1190might be incorporated into the processor 1110.

The processor 1110 executes instructions, codes, computer programs, orscripts that it might access from the network connectivity devices 1120,RAM 1130, ROM 1140, or secondary storage 1150 (which might includevarious disk-based systems such as hard disk, floppy disk, or opticaldisk). While only one CPU 1110 is shown, multiple processors may bepresent. Thus, while instructions may be discussed as being executed bya processor, the instructions may be executed simultaneously, serially,or otherwise by one or multiple processors. The processor 1110 may beimplemented as one or more CPU chips.

The network connectivity devices 1120 may take the form of modems, modembanks, Ethernet devices, universal serial bus (USB) interface devices,serial interfaces, token ring devices, fiber distributed data interface(FDDI) devices, wireless local area network (WLAN) devices, radiotransceiver devices such as code division multiple access (CDMA)devices, global system for mobile communications (GSM) radio transceiverdevices, worldwide interoperability for microwave access (WiMAX)devices, and/or other well-known devices for connecting to networks.These network connectivity devices 1120 may enable the processor 1110 tocommunicate with the Internet or one or more telecommunications networksor other networks from which the processor 1110 might receiveinformation or to which the processor 1110 might output information. Thenetwork connectivity devices 1120 might also include one or moretransceiver components 1125 capable of transmitting and/or receivingdata wirelessly.

The RAM 1130 might be used to store volatile data and perhaps to storeinstructions that are executed by the processor 1110. The ROM 1140 is anon-volatile memory device that typically has a smaller memory capacitythan the memory capacity of the secondary storage 1150. ROM 1140 mightbe used to store instructions and perhaps data that are read duringexecution of the instructions. Access to both RAM 1130 and ROM 1140 istypically faster than to secondary storage 1150. The secondary storage1150 is typically comprised of one or more disk drives or tape drivesand might be used for non-volatile storage of data or as an over-flowdata storage device if RAM 1130 is not large enough to hold all workingdata. Secondary storage 1150 may be used to store programs that areloaded into RAM 1130 when such programs are selected for execution.

The I/O devices 1160 may include liquid crystal displays (LCDs), touchscreen displays, keyboards, keypads, switches, dials, mice, track balls,voice recognizers, card readers, paper tape readers, printers, videomonitors, or other well-known input/output devices. Also, thetransceiver 1125 might be considered to be a component of the I/Odevices 1160 instead of or in addition to being a component of thenetwork connectivity devices 1120. One or more of the above system 1115components may be referred to as “component” or “components” herein.

The embodiments provide for a relay node including one or morecomponents configured to encode a message to be transmitted to an accessnode, the message used to identify the relay node as a relay node duringinitialization of the relay node. The embodiments also provide a methodand a computer readable storage medium storing code to implement themethod to encode a message to be transmitted to an access node, themessage used to identify the relay node as a relay node duringinitialization of the relay node. The embodiments further provide forone or more components configured to decode a message received from arelay node and, from the message, to identify the relay node as a relaynode.

In yet other embodiments, a relay node is provided that includes one ormore components configured to measure a signal strength of soundingreference signals (SRS) received from a mobile station, and in responseto the signal strength being above a predetermined threshold, totransmit a first request to an access node. The first request is for theaccess node to associate the mobile station with the relay node. Theembodiments also provide for a method for implementing the above.

In yet other embodiments, an access node is provided that includes oneor more components configured to receive a first request to associate amobile station with a relay node. The first request is transmitted as aresult of the relay node determining that a signal strength of asounding reference signal (SRS) received from the mobile station isabove a predetermined threshold.

The embodiments also provide for an access node including one or morecomponents configured to receive a random access channel (RACH)transmission from a mobile station, detect the signal strength of thereceived RACH transmission, and receive a relayed RACH report from arelay node. The embodiments also provide for a method for implementingthe above.

In yet other embodiments, a relay node is provided that includes one ormore components configured to transmit a relayed random access channel(RACH) report to an access node, the relayed RACH report including asignal quality of a RACH received by the relay node from a mobilestation.

While several embodiments have been provided in the present disclosure,it should be understood that the disclosed systems and methods may beembodied in many other specific forms without departing from the spiritor scope of the present disclosure. The present examples are to beconsidered as illustrative and not restrictive, and the intention is notto be limited to the details given herein. For example, the variouselements or components may be combined or integrated in another systemor certain features may be omitted, or not implemented.

Also, techniques, systems, subsystems and methods described andillustrated in the various embodiments as discrete or separate may becombined or integrated with other systems, modules, techniques, ormethods without departing from the scope of the present disclosure.Other items shown or discussed as coupled or directly coupled orcommunicating with each other may be indirectly coupled or communicatingthrough some interface, device, or intermediate component, whetherelectrically, mechanically, or otherwise. Other examples of changes,substitutions, and alterations are ascertainable by one skilled in theart and could be made without departing from the spirit and scopedisclosed herein.

What is claimed is:
 1. A relay node comprising: one or more componentsconfigured to measure a signal strength of sounding reference signals(SRS) received from a mobile station, and in response to the signalstrength being above a predetermined threshold, to transmit a firstrequest to an access node, wherein the first request is for the accessnode to associate the mobile station with the relay node, wherein theone or more components are further configured to transmit a secondrequest to the access node after the first request, wherein the secondrequest is transmitted in response to the signal strength falling belowa second predetermined threshold, and wherein the second request is forthe access node to disassociate the mobile station with the relay node.2. The relay node of claim 1 wherein the one or more components arefurther configured to periodically measure the signal strength of theSRS received from the mobile station.
 3. The relay node of claim 1wherein the one or more components are further configured to generate ameasurement report of the signal strength upon satisfaction of acondition set by the access node.
 4. The relay node of claim 3 whereinthe condition comprises at least one of a threshold of the signalstrength or an expiration of a timer.
 5. The relay node of claim 1wherein the first request establishes one type of association selectedfrom the group consisting of: the mobile station being associated withthe access node only, the mobile station being associated with one ormore relay nodes only, and the mobile station being associated with boththe access node and the one or more relay nodes.
 6. A method implementedin a relay node, the method comprising: measuring a signal strength ofsounding reference signals (SRS) received from a mobile station, and inresponse to the signal strength being above a predetermined threshold,transmitting a first request to an access node, wherein the firstrequest is for the access node to associate the mobile station with therelay node; and transmitting a second request to the access node afterthe first request, wherein the second request is transmitted in responseto the signal strength falling below a second predetermined threshold,and wherein the second request is for the access node to disassociatethe mobile station with the relay node.
 7. The method of claim 6 furthercomprising: periodically measuring the signal strength.
 8. The method ofclaim 6 further comprising: generating a measurement report of thesignal strength upon satisfaction of a condition set by the access node.9. The method of claim 8 wherein the condition comprises at least one ofa threshold of the signal strength or an expiration of a timer.
 10. Themethod of claim 6 wherein the first request establishes one type ofassociation selected from the group consisting of: the mobile stationbeing associated with the access node only, the mobile station beingassociated with one or more relay nodes only, and the mobile stationbeing associated with both the access node and the one or more relaynodes.
 11. An access node comprising: one or more components configuredto receive a first request to associate a mobile station with a relaynode, the first request being transmitted as a result of the relay nodedetermining that a signal strength of a sounding reference signal (SRS)received from the mobile station is above a predetermined threshold,wherein the access node receives a second request to disassociate themobile station with the relay node, the second request being transmittedin response to the signal strength falling below a second predeterminedthreshold.
 12. The access node of claim 11 wherein the access node setsa condition upon satisfaction of which the relay node generates ameasurement report of the signal strength.
 13. The access node of claim12 wherein the condition comprises at least one of a threshold of thesignal strength or an expiration of a timer.
 14. The access node ofclaim 11 wherein the first request establishes one type of associationselected from the group consisting of: the mobile station beingassociated with the access node only, the mobile station beingassociated with one or more relay nodes only, and the mobile stationbeing associated with both the access node and the one or more relaynodes.
 15. An access node comprising: one or more components configuredto receive a random access channel (RACH) transmission from a mobilestation, detect the signal strength of the received RACH transmission,and receive a relayed RACH report from a relay node; and one or morecomponents configured to encode a message to be transmitted to themobile station, wherein the message is encoded to instruct the mobilestation to perform RACH preamble transmission using a procedure which isless than a full random access procedure.
 16. The access node of claim15, wherein the relayed RACH report includes a signal quality of theRACH received by the relay node from the mobile station.
 17. The accessnode of claim 16, further comprising one or more components configuredto determine an association of the mobile station to the relay nodebased on the signal quality of the RACH received from the mobile stationand a signal strength indicated in the relayed RACH report.
 18. Theaccess node of claim 15, wherein the message is at least one of aphysical downlink control channel (PDCCH) order, a media access layer(MAC) control element, or a radio resource control (RRC) signaling. 19.The access node of claim 15 wherein the access node comprises anenhanced node B (eNB).
 20. A method implemented in an access node, themethod comprising: the access node receiving a random access channel(RACH) transmission from a mobile station; the access node detecting thesignal strength of the received RACH transmission; the access nodereceiving a relayed RACH report from a relay node; and the access nodeencoding a message to be transmitted to the mobile station, wherein themessage is encoded to instruct the mobile station to perform RACHpreamble transmission using a procedure which is less than a full randomaccess procedure.
 21. The method of claim 20, wherein the relayed RACHreport includes a signal quality of the RACH received by the relay nodefrom the mobile station.
 22. The method of claim 21, further comprisingthe access node determining an association of the mobile station to therelay node based on the signal quality of the RACH received from themobile station and a signal strength indicated in the relayed RACHreport.
 23. The method of claim 20, wherein the message is at least oneof a physical downlink control channel (PDCCH) order, a media accesslayer (MAC) control element, or a radio resource control (RRC)signaling.
 24. The method of claim 20 wherein the access node comprisesan enhanced node B (eNB).